For a semiconductor memory device, a structure in which memory cells are three-dimensionally arranged has been proposed recently. In this structure, a hole penetrating a stacked body including a plurality of electrode films stacked and a slit splitting the stacked body are formed.
In the hole, a memory film is formed. Further, a sacrificial film is formed at an upper part of a source line located below the stack. The sacrificial film is removed to expose a part of the memory film, a part of the exposed memory film is removed, and a conductive layer is formed at a removal part of the sacrificial film. This electrically connects a channel layer in a memory hole to the source line.
Since the hole needs to penetrate the sacrificial film (conductive layer), a thin sacrificial film is desirable in consideration of processing variation. Contrarily, since the slit needs to terminate in the sacrificial film (conductive layer), a thick sacrificial film is desirable in consideration of processing variation.
However, since the thickness of the sacrificial film has been conventionally uniform, it is difficult to absorb the processing variations of both the hole and the slit. In the case where a necessary depth is not ensured regarding the processing of the hole and the slit, the reliability as the semiconductor memory device may become insufficient.
Embodiments of the present invention provide a semiconductor memory device capable of improving the reliability and a manufacturing method thereof.